Optometry Admission Test (OAT) Practice

What is the end product of anaerobic respiration in yeast?

1. Glucose

2. Alcohol (ethanol)

3. Carbon dioxide

4. Lactic acid

The correct answer is: Alcohol (ethanol)

The end product of anaerobic respiration in yeast is alcohol, specifically ethanol. During anaerobic respiration, yeast cells convert glucose into energy when oxygen is not available. This process is known as fermentation. In this anaerobic pathway, glucose is broken down into pyruvate through glycolysis, and then the pyruvate undergoes a series of reactions to produce ethanol and carbon dioxide. The production of ethanol is a crucial aspect of both the energy metabolism of yeast and the fermentation process used in brewing and baking. The carbon dioxide released during this process is responsible for the carbonation in beverages and the leavening of bread. Understanding the role of ethanol in this metabolic pathway highlights its importance in various industries, especially in the production of alcoholic beverages and biofuels. In contrast, while other substances like lactic acid are products of anaerobic respiration in different organisms (such as muscle cells in animals), they are not produced by yeast. This distinction helps clarify the specific metabolic pathways employed by various organisms under anaerobic conditions.